Gavin,
The smoke thing is a non-issue! This photo was not about smoke. When we did this, you don't see the diesel in the video so its not something we "Requested" as a railfan thing. In fact we did not request anything abnormal for the 484 run either. While it went unstated(between the C&TS and the sponsors), we just wanted a typical run!
There were plenty of times the stack was clean. We were after the scenery and the train in it 100% of the time, including continuous stack talk. No other place I know of can produce that kind of excitement for such a long period of time without being a cog railroad perhaps.
The C&TS and D&S both have great scenery, while each is different. However, its the 4% grade which makes the Chama-Cumbres section so attractive, at least to me!